A grand jury investigation is underway in the Trump-Russia probe -- here's how they work

Grand juries have a long history in the American legal system. They are a large group of jurors assembled and tasked with investigating suspected criminal conduct.

The most recent and most public example of grand jury proceedings can be found in the investigation of Russia’s interference in the 2016 US election.

The Wall Street Journal reported on Thursday that special counsel Robert Mueller impaneled a grand jury weeks ago, signalling that the inquiry into Russian influence and possible collusion with the Trump campaign continues to move forward.

Here’s what a grand jury does:

Review evidence, including witness testimony on behalf of prosecutors in the investigation of potential criminal conduct.

Issue subpoenas for more evidence, documents, and sworn testimony.

If grand juries decide there is enough evidence to charge the accused with a crime, they vote on whether to indict the person, opening the door for a formal trial.

Grand jury proceedings are conducted in secret. There are no judges and no defence counsel is involved No members of the public or press are privy to the grand jury’s activities.

Grand juries tend to have broad mandates, depending on the investigation, but they cannot:

Formally charge anyone with a crime.

Convict the accused. A grand jury indictment does not automatically infer that a suspect is guilty of a crime.

Impose a sentence or punishment on anyone.

Grand juries do not obtain or review evidence from defence counsel. The defence has to wait until a trial to speak, if a trial is scheduled.

Historic grand jury proceedings

Richard Nixon faced a grand jury in June 1975 in the heat of the Watergate scandal. Nixon accused prosecutors of trying to “destroy” him, according to transcripts of his testimony, released by the Nixon Presidential Library and Museum.

Nixon had already been pardoned by President Gerald Ford by the time he testified. That pardon gave him immunity, but the specter of perjury charges still loomed during the proceedings. Many of Nixon’s comments were short and he often answered that he “did not recall” certain events.

President Bill Clinton testified for several hours before a grand jury in August 1998, at the end of an independent counsel investigation into the Whitewater real-estate case that lasted four years. Clinton was called before the grand jury after being accused of perjury by then-independent counsel Kenneth Starr for his denials under oath of sexual misconduct with then-White House intern, Monica Lewinsky.

President Trump has frequently railed against Mueller’s investigation, and has, at times, floated the possibility of seeking his dismissal. Those suggestions have been met with stern warnings from both Republicans and Democrats, who say that Trump’s problems would only worsen if he were to disrupt the Russia probe.

Former federal prosecutor Alex Whiting previously wrote that grand jury investigations can last for years while prosecutors examine leads and gather evidence, as was the case in the Nixon and Clinton proceedings.

It may be a while before we learn any of the details about the Trump-Russia investigation, and longer still before it reaches a conclusion.